old 3.0 replacing a newer 3.0 ?'s

I have a 95 sea ray 170 with a 99 mercruiser 3.0 that went bad mostly because of my own stupidity. i bought an older 80's 3.0 that runs beautifully, was removed from a rotted old boat and mounted to a pallet at a marine shop where they hooked it up to fuel, water and a "test box" with several gauges and an ignition source. the motor runs beautiful and smooth and not a single knock or burp. I am going to bring it to a guy that has serviced my grandparents boats for years and he is very good but the more work i can do the less he will charge me.

my only issue is with the wiring harness. the old one on the "new" engine has a different plug layout than the newer "old" engine that is being removed. would it be easier to just build an adapter on my own if i can find one that i can cut up or can i find an adapter plug to go from my boat ( newer style harness ) to the engine ( older style harness ) ?

thanks experts. i appreciate your time. the boat has been sitting for 3 years covered because i was in school and getting married and buying a house and starting a new career. now it's time to get my boat back. it's small but it's a great little boat and was the boat i learned to water ski and wake-board behind. it holds a lot of sentimental value to me.

Re: old 3.0 replacing a newer 3.0 ?'s

strip it down to block and heads, then build back up. the long block is the same, however as you mentioned, the other "stuff" has changed over the years.

Re: old 3.0 replacing a newer 3.0 ?'s

Not exactly what I wanted to hear. everything works perfectly I just need to swap over my power steering (super easy) and have to do something with the engine harness. need to know what to do with the harness.

Re: old 3.0 replacing a newer 3.0 ?'s

If it were mine I'd get wiring diagrams for both engines and compare them to see if it were possable to rewire the "new" engine to conform to the wiring in the boat/"old" engine. If I'm not terrably mistaken, and I may be, it's possable to change the pin position in the connector. So maybe you can simply redo the connector on the "new" engine to work.
However, it may not be possable as 10+ years for marine engines can mean a lot of changes...
But I'd certainly be comparing the two to see if it is something that might work.
Failing that, you can always go with the "strip it down & rebuild it" method.

Re: old 3.0 replacing a newer 3.0 ?'s

Thanks, that's pretty much what I was thinking had to be done. I was just Hoping there was an already available adapter in magic land I could find. I have ordered a manual but that could take a month to get here. Anywhere online to get them a wiring diagram for both?

Re: old 3.0 replacing a newer 3.0 ?'s

Why don't you just swap the electricals off the motor in the boat onto the replacement ? Dizzy may be different along with the alternator and possibly the carb.

Re: old 3.0 replacing a newer 3.0 ?'s

The distributor is different, more lime a can style coil with just a pos and neg and coil wire. The bad motor has a seperate harness going from the coil to dist. Cap. The main harness plug is different but I might just swap it with the bad motor's mai. harness plug.